Implanter calibration

ABSTRACT

The present disclosure relates to a method includes generating ions with an ion source of an ion implantation apparatus based on an ion implantation recipe. The method includes accelerating the generated ions based on an ion energy setting in the ion implantation recipe and determining an energy spectrum of the accelerated ions. The method also includes analyzing a relationship between the determined energy spectrum and the ion energy setting. The method further includes adjusting at least one parameter of a final energy magnet (FEM) of the ion implantation apparatus based on the analyzed relationship.

This application is a continuation of U.S. patent application Ser. No.16/539,513, titled “Implanter Calibration,” which was filed on Aug. 13,2019, which claims the benefit of U.S. Provisional Patent ApplicationNo. 62/718,423, titled “System and Method for Calibrating High EnergyImplanters,” which was filed on Aug. 14, 2018, all of which areincorporated herein by reference in their entireties.

BACKGROUND

High energy implantation is an important process in forming dopedlayers, either deeply in a substrate or through thick overlying layersand into the substrate. In complementary metal-oxide-semiconductor(CMOS) image sensor technology for very-large-scale integration (VLSI)applications, high energy implantation is a key process to form a deepjunction structure between p-type and n-type diffusion profiles that areused as photodiode regions. High energy implantation also offers anadvantage of forming n-well or p-well after a high temperature for fieldoxidation process.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. Inaccordance with the common practice in the industry, various featuresare not drawn to scale. In fact, the dimensions of the various featuresmay be arbitrarily increased or reduced for clarity of illustration anddiscussion.

FIG. 1 illustrates a semiconductor device having multiple doped regionsformed using a high energy implantation apparatus, in accordance withsome embodiments.

FIG. 2 illustrates an ion implanter, in accordance with someembodiments.

FIG. 3 illustrates exemplary ion implantation calibration recipes, inaccordance with some embodiments.

FIG. 4 illustrates a flow diagram of an exemplary method for calibratingone or more ion implanters, in accordance with some embodiments.

FIGS. 5-8 illustrate ion energy spectrums after calibration for variouscalibration recipes, in accordance with some embodiments.

FIGS. 9-10 illustrate exemplary results of wafer acceptance testsshowing improved agreements between multiple ion implanters aftercalibration processes, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over a second feature in the description that followsmay include embodiments in which the first and second features areformed in contact (e.g., in direct or physical contact), and may alsoinclude embodiments in which additional features are disposed betweenthe first and second features, such that the first and second featuresare not in contact (e.g., in direct or physical contact). In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition does not in itself dictate arelationship between the various embodiments and/or configurationsdiscussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The term “nominal” as used herein refers to a desired, or target, valueof a characteristic or parameter for a component or a process operation,set during the design phase of a product or a process, together with arange of values above and/or below the desired value. The range ofvalues can be due to slight variations in manufacturing processes ortolerances.

In some embodiments, the terms “about” and “substantially” as usedherein indicates the value of a given quantity that can vary based on aparticular technology node associated with the subject semiconductordevice, such as within ±5% of a target (or intended) value (e.g., ±1%,±2%, ±3%, ±4%, or ±5% of the value).

The term “deep junction structure” refers to a junction region deeplyformed (e.g., between wells or between wells and a substrate) in asemiconductor substrate, such as a deep PN junction formed between ann-type region (e.g., an n-well) and a p-type region (e.g., a p-well orp-type substrate), which can be used in a wide variety of applicationsincluding, for example, pinned photodiode, CMOS image sensor, lightsensing device, SRAM cell, DRAM cell, RAM or ROM cell, and the like.

Ion implantation is a process in the manufacturing of semiconductordevices that provides a controlled method of changing electricalcharacteristics of selected regions within a semiconductor device. Ionimplantation uses an ion implanter to generate ions of a nominal dopantand then accelerates the ions to an appropriate energy level. Onceaccelerated, the ions are transported by the ion implanter along an ionbeam to impact and implant into selected regions of a semiconductorwafer.

High energy implantation is a technology used to form doped layers,either deep in the substrate or through thick overlying layers into thesubstrate. As used throughout this disclosure, the term “high energyimplantation” refers to an ion implantation process requiring highenergy (e.g., between about 200 KV and about 3000 KV) and results inhigh ion penetration depths. Ion energy control of high energyimplantation is becoming increasingly important as device size continuesto shrink. Accurate calibration of high energy implanters (HEI) iscritical for achieving a nominal doped profile on selected regions ofsubstrates. In addition, accurate calibration for multiple high energyimplanters can provide the improved yield in wafer acceptance tests(WATs). In contrast, ion implantation apparatus without calibration canlead to variations and dopant profile mismatches between multipleimplanters.

Various embodiments in accordance with this disclosure describe systemsand methods for calibrating implanters (e.g., high energy implanters)for use in semiconductor wafer processing, and more particularly tosystems and methods for modifying and calibrating final energy magnet(FEM) of an implantation apparatus. The present disclosure providessystems and methods for improving WATs by determining energy gapsbetween a recipe energy and determined energy of an ion beam at a finalenergy magnet (FEM), and calibrating the implantation apparatus based onthe energy gaps. The calibration system determines target mass and ionbeam energy after ions are accelerated and selected by an analysismagnet unit (AMU). The calibration system further determines a totalenergy amount when ion beams pass through a linear accelerator andthrough the FEM. The calibration system further determines an error gapbetween nominal energy specified in a calibration recipe and peak energyof the ion beam energy spectrum determined at the FEM. In someembodiments, the calibration system is configured to adjust at least oneparameter of the final energy magnet such that the energy difference orerror gap is within about 1% of the energy spectrum specified by thecalibration recipe or energy spectrum detected at the AMU. Thecalibration system can be implemented in one or more implantationapparatuses and maintain good agreement across a group of implanters.For example, a centralized calibration system can be configured tocompare secondary ion mass spectrometry (SIMS) measurement data of ionpenetration depths from multiple implanters and determine implantationuniformity. In some embodiments, uniformity can be achieved whenpenetration depth of each implanter obtained from the SIMS measurementdata across the group of implanters is within 3% of the averagepenetration depth among the group of implanters. The centralizedcalibration system can be further configured to instruct the calibrationsystem of the implanter having abnormal measurements to adjust one ormore parameters of the final energy magnet such that its implantationdepth is within 3% of the average penetration depths in the group.Although various embodiments disclosed in the present disclosure aredirected to high energy implantation apparatus, it should be noted thatthe various embodiments can also be applied to other implantationapparatus using lower ion energy (e.g., between 1 keV and 30 keV).

FIG. 1 is a cross-sectional view of an exemplary semiconductor device100 with various doped regions formed using an implantation apparatus,in accordance with some embodiments of the present disclosure. In someembodiments, the implantation apparatus can be a high energyimplantation apparatus. Exemplary semiconductor device 100 includes asubstrate 102, shallow trench isolation structures 124, gate electrode132, gate spacers 140, gate dielectric layer 130, lightly-doped regions134, source/drain regions 142, pocket implantation regions 131,threshold voltage implantation region 133, anti-punch-throughimplantation region 144, and well implantation region 146. Accuratecalibration of the implantation apparatus is critical for achieving thedesired doped profile in the above listed semiconductor regions. Withoutaccurate calibration, incorrect dopant profiles would result, whichcould in turn lead to low device quality and yield. For example,incorrect dopant profile can lead to failure of WATs. Exemplarysemiconductor device 100 can further include other suitable structuresand are not illustrated in FIG. 1 for simplicity. Components ofexemplary semiconductor device 100 are for illustration purposes and arenot drawn to scale.

Substrate 102 can be formed using bulk silicon. In some embodiments,substrate 102 can be a p-type substrate, such as a silicon materialdoped with a p-type dopant (e.g., boron). In some embodiments, substrate102 can be an n-type substrate, such as a silicon material doped with ann-type dopant (e.g., phosphorous or arsenic). In some embodiments,substrate 102 can include, germanium, diamond, a compound semiconductor,an alloy semiconductor, a silicon-on-insulator (SOI) structure, anyother suitable material, or combinations thereof. For example, thecompound semiconductor can include silicon carbide, gallium arsenide,gallium phosphide, indium phosphide, indium arsenide, and/or indiumantimonide, and the alloy semiconductor can include SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and/or GaInAsP.

Shallow trench isolation structures 124 can be formed in substrate 102and between semiconductor devices to avoid crosstalk. For example,shallow trench isolation structures 124 are formed in substrate 102 andcan be made of a dielectric material, such as silicon oxide,spin-on-glass, silicon nitride, silicon oxynitride, fluorine-dopedsilicate glass (FSG), a low-k dielectric material, any other suitableinsulating material, or combinations thereof. In some embodiments,shallow trench isolation structures 124 can be shallow trench isolation(STI) structures formed by etching trenches in substrate 102. Thetrenches can be filled with insulating material, followed by an optionalchemical-mechanical polishing (CMP) and etch-back process. Otherfabrication techniques for shallow trench isolation structures 124 arepossible. Shallow trench isolation structures 124 can include amulti-layer structure, such as a structure with one or more linerlayers.

Gate dielectric layer 130 can be formed on a top surface of substrate102, in accordance with some embodiments of the present disclosure. Insome embodiments, gate dielectric layer 130 can include a high-kdielectric layer (e.g., dielectric constant greater than 3.9). Gatedielectric layer 130 can be formed through a blanket deposition followedby a patterning and etching process. In some embodiments, gatedielectric layer 130 can be a silicon oxide layer (e.g., silicondioxide). In some embodiments, gate dielectric layer 130 can include ahigh-k material, such as hafnium oxide, lanthanum oxide, aluminum oxide,zirconium oxide, silicon nitride, or other suitable high-k materials.Gate dielectric layer 130 can include a plurality of layers and can beformed using a deposition process, such as chemical vapor deposition(CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD),physical vapor deposition (PVD), any other suitable process, orcombinations thereof.

Gate electrode 132 is a conductive structure formed on substrate 102, inaccordance with some embodiments of the present disclosure. Gateelectrode 132 can include conducting materials such as tungsten,titanium, tantalum, copper, titanium nitride, tantalum nitride,molybdenum, other suitable metal or metal alloys, or combinationsthereof. In some embodiments, gate electrode 132 can include dopedpolysilicon material. In some embodiments, gate electrode 132 can alsoinclude a diffusion barrier layer, such as titanium nitride (TiN) andtitanium silicon nitride (TiSiN). In some embodiments, gate electrode132 can further include a work-function layer, such as TiN and titaniumaluminum (TiAl) for n-type devices and tantalum nitride (TaN) and TiAlfor p-type devices. In some embodiments, forming gate electrode 132 canbe performed using an ALD process, a CVD process, a PVD process, othersuitable deposition processes, or combinations thereof.

Lightly-doped regions 134 are formed in substrate 102, in accordancewith some embodiments of the present disclosure. Lightly-doped regions134 can be referred to as “source and drain extension regions.” In someembodiments, lightly-doped regions 134 can be formed using a high energyimplantation apparatus calibrated using the devices and methodsdescribed in the present disclosure. An implantation is performed tointroduce n-type impurities into substrate 102 to form lightly-dopedregions 134. N-type impurities include any suitable impurities, such asarsenic, phosphorous, any other suitable impurities, or combinationsthereof. Gate electrode 132 can act as mask so that lightly-dopedregions 134 can be formed substantially aligned with the edges of gateelectrode 132.

Pocket regions 131 can be formed in substrate 102, in accordance withsome embodiments of the present disclosure. In some embodiments, pocketregions 131 can be formed using high energy implantation apparatuscalibrated using the devices and methods described in the presentdisclosure. Pocket regions 131 can be formed by tilt implanting p-typeimpurities, such as boron, indium, any other suitable impurities, orcombinations thereof. In some embodiments, impurities can be implantedto a dosage of between about 5×10¹²/cm² and about 5×10¹⁴/cm² (e.g.,5×10¹²/cm² and 5×10¹⁴/cm²). In some embodiments, different dosages canbe used.

Source/drain regions 142 are formed in substrate 102, in accordance withsome embodiments of the present disclosure. In some embodiments,source/drain regions 142 can be formed using a high energy implantationapparatus calibrated using the devices and methods described in thepresent disclosure. In some embodiments, source/drain regions 142 areformed by implanting n-type impurities. A photoresist layer can beformed and an implantation is performed to introduce n-type impuritiesinto regions not covered by the photoresist layer. In some embodiments,the implanted impurities include phosphorous or arsenic. In someembodiments, the implanted impurities include both arsenic andphosphorous. In some embodiments, the dosage of arsenic can be lowerthan the dosage of phosphorous. In some embodiments, the dosage ofarsenic is less than about 30 percent of the dosage of phosphorous. Theimplanted impurity can have a greater concentration closer to thesurface of source/drain regions 142, and a lighter concentration deeperin source/drain regions 142. To achieve such a profile, multipleimplantations can be performed. In some embodiments, one of theimplantations can have a dosage of between about 1×10¹⁵/cm² and about6×10¹⁵/cm² and implanted with an energy between about 0.5 keV and about10 keV. In some embodiments, implantation can be performed using adosage of between about 5×10¹³/cm² and about 1×10¹⁵/cm² and implantedwith an energy of between about 1 keV and about 30 keV. Each of theimplantation process can be may be performed vertically or tilted. Forexample, a tilt angle can be less than about 15°.

Anti-punch-through implantation region 144 is formed in substrate 102,in accordance with some embodiments of the present disclosure. In someembodiments, anti-punch-through implantation region 144 can be formedusing a high energy implantation apparatus calibrated using the devicesand methods described in the present disclosure. Anti-punch-throughimplantation region 144 can be a blanket implantation region below achannel region of semiconductor device 100. Anti-punch-throughimplantation region 144 can reduce sub-threshold source-to-drain leakageand a drain-induced barrier lowering effect. Anti-punch-throughimplantation region 144 can be an n-type region or a p-type region. Insome embodiments, an n-type anti-punch-through implantation region 144can be obtained by doping with an n-type dopant, such as arsenic,phosphorous, antimony, any suitable n-type dopant, or combinationsthereof. In some embodiments, p-type anti-punch-through implantationregion 144 can be obtained by doping with a p-type dopant, such asboron, boron fluorine, any suitable p-type dopant, or combinationsthereof. In some embodiments, the ion implantation process can beoperated under power in a range from about 3 keV to about 7 keV (e.g., 3keV to 7 keV) on the substrate surface. In some embodiments, the ionimplantation process can be operated within a power range between about7 keV and about 50 keV (e.g., 7 keV to 50 keV).

Well implantation region 146 is formed in substrate 102, in accordancewith some embodiments of the present disclosure. In some embodiments,well implantation region 146 can be formed using a high energyimplantation apparatus calibrated using the devices and methodsdescribed in the present disclosure. Well implantation region 146 can beformed using a high energy ion implantation process and employing anysuitable n-type or p-type dopant. Therefore, the well implantationprocess may form an n-well or a p-well in semiconductor device 100. Insome embodiments, the n-type dopant can include arsenic, phosphorous,any suitable n-type dopant material, or combinations thereof. In someembodiments, the p-type dopant can include boron, aluminum, gallium,indium, any suitable p-type dopant material, or combinations thereof.

In some embodiments, implantation processes can form other suitableregions in semiconductor device 100. For example, high energyimplantation processes employing n-type or p-type dopants can formhigh-voltage doped regions, which may be referred to as “n-channel drift(NHV) regions” or “p-channel drift (PHV) regions”; doped sinker regions;a reduced surface field (RESURF) layer; and/or or other doped extensionand/or well regions.

FIG. 2 illustrates an ion implanter 200, in accordance with variousembodiments of the present disclosure. In some embodiments, ionimplanter 200 can be a high energy ion implantation apparatus. Ionimplanter 200 includes an ion source 203, an analysis magnet unit 205,an upstream scanner device 207, a linear accelerator 209, extractionelectrode 240, suppression electrode 242, a final energy magnet 211, ascanning device 212, an end station 213, a wafer handling unit 215, anda controller 217 to control the calibration and operation of ionimplanter 200.

Ion source 203 can accelerate electrons generated in a plasma dischargeto impact neutral gaseous source species, thereby forming source ionswhich are accelerated along an ion beam line to bombard a target, suchas a semiconductor wafer. In some embodiments, ion source 203 generatesan ion beam 204 that includes ions having a range of charge-to-massratio and ion energy, and only a certain range of ions are suitable forimplantation. For example, ion source 203 can be configured to generateboron (B) ions, arsenic (As) ions, argon (Ar) ions, xenon (Xe) ions, andany other suitable ions. In some embodiments, ion source 203 cangenerate B⁺ ions, Ar⁺ ions, and any other suitable ions. In someembodiments, ion source 203 can generate xenon ions with differentcharges. For example, ion source 203 can generate Xe⁺, Xe²⁺, or Xe³⁺ions. In some embodiments, ion source 203 can also include a DCaccelerator for accelerating generated ions. Therefore, ion source 203can generate ions having different ion energy using the DC acceleratorand in accordance to ion implantation recipes, for example, Xe³⁺ ionshaving 70 keV or 90 keV energy can be generated by ion source 203.

Extraction electrode 240 can be used for extracting charged ions fromion beam 204 that combine downstream to form a broad beam. Individualelectrodes of suppression electrodes 242 in close proximity toextraction electrode 240 can be biased to inhibit back streaming ofneutralizing electrons close to ion source 203 or back to extractionelectrode 240.

Analysis magnet unit 205 receives ion beam 204 and separates ions havinga desired charge-to-mass ratio for implantation from those ions havingan undesired charge-to-mass ratio, according to some embodiments of thepresent disclosure. Analysis magnet unit 205 includes a pre-analyzingmagnet with tunable magnetic field. Ions having identical energies butdifferent masses experience a different magnetic force as they passthrough the magnetic field due to their differing masses therebyaltering their pathways. As a result, only those desired ions of aparticular mass-to-charge ratio pass through a prepositioned orifice inthe pre-analyzing magnet. Once a coherent ion beam 221 of suitablecharge-to-mass ratio is obtained, coherent ion beam 221 is sent tolinear accelerator 209. In some embodiments, an upstream scanner device207 is located downstream of analysis magnet unit 205. Upstream scannerdevice 207 is configured to scan coherent ion beam 221 and generate anion energy spectrum with reference to the beam current of analysismagnet unit 205 and also determine a peak energy of the ion beam. Insome embodiments, the ion energy spectrum and peak energy can calibrateion implanter 200.

Linear accelerator 209 is used to impart additional energy to coherention beam 221 as it passes through linear accelerator 209. In someembodiments, linear accelerator 209 is turned off during calibrationprocesses described in the present disclosure. Linear accelerator 209imparts additional energy using a series of electrodes (not shown) thatgenerate an electromagnetic field which, when the coherent ion beam 221passes through the electromagnetic field, works to accelerate ions incoherent ion beam 221. Linear accelerator 209 can vary electromagneticfields periodically with time or adjust the phase of the electromagneticfields to accommodate ions with different atomic numbers as well as ionshaving different initial speeds.

Final energy magnet 211 receives coherent ion beam 221 after linearaccelerator 209 and the ion energy delivered by ion implanter 200 isdetermined by one or more parameter settings of final energy magnet 211.Final energy magnet 211 can remove ions or neutral particles that havebeen generated with an incorrect energy during the accelerationprocesses. Final energy magnet 211 can be set to provide a particularmagnetic field corresponding to a desired ion type by adjusting a finalenergy magnet current that flows through one or more sets of conductivecoils. Accurate calibration (e.g., within 1%, 3%, or any nominalpredetermined value) of ion implanters (e.g., high energy ionimplanters) is based on the successful calibration of the final energymagnet. The success of final energy magnet calibration process iscritical for achieving the desired doped profile on selected regions ofsubstrates. Accurate calibration for multiple high energy implanters canalso improve yield in wafer acceptance tests. The calibration system canbe implemented on one or more high energy implantation apparatus andmaintain good agreement across all implanters.

Scanning device 212 is located downstream of final energy magnet 211.Scanning device 212 is configured to scan the ion beam and generate anion energy spectrum with reference to the beam control current of finalenergy magnet 211. For example, scanning device 212 can provide ionenergy spectrums with reference to the maximum ion beam control currentfor final energy magnet. In some embodiments, scanning device 212 can bea probe incorporated in final energy magnet 211. For example, scanningdevice 212 can be a gauss probe located between poles of final energymagnet 211. In some embodiments, scanning device 212 includes a pair ofcoils for generating an electromagnetic field that varies in time inaccordance with a frequency of the power supplied to the pair of coils.As the ion beam is passed between the pair of coils, the time-varyingelectromagnetic field deflects ions in the ion beam (e.g., according tothe “left-hand rule” or the “right-hand rule”). As a result, the ionbeam is reciprocally deflected, i.e., scanned, in the scanning directionbetween the pair of coils.

End station 213 can house wafer handling unit 215 which handles wafer223. Wafer 223 will be implanted with ions from coherent ion beam 221.Wafer handling unit 215 is utilized to move wafer 223 in relation tocoherent ion beam 221 so as to illuminate different sections of wafer223 with coherent ion beam 221. For example, wafer handling unit 215 caninclude two motors (not shown) that are used to control the position ofwafer 223 in at least two directions, such as an x-direction and ay-direction, relative to coherent ion beam 221. In some embodiments,other methods and/or structures for moving wafer 223 in relation tocoherent ion beam 221 is merely one exemplary method of illuminatingdifferent sections of wafer 223 with coherent ion beam 221. Othersuitable methods can be used for moving wafers. For example, electrodescan be deflected along the path of coherent ion beam 221 to shift adirection of coherent ion beam 221 in relation to wafer 223 instead ofshifting the wafer 223 in relation to coherent ion beam 221. In someembodiments, a multiple wafer rotating system can be used to illuminatemultiple wafers in order, or angular implantation methods can also beutilized.

Controller 217 can control the calibration and operating parameters ofion implanter 200. Controller 217 can load, store, and controlparameters associated with the calibration and operation of ionimplanter 200, such as nominal ion beam current, final energy magnetspectrum, current supplied to the accelerator electrodes, currentsupplied to the final energy magnet, and/or any other suitableparameters or operations. For example, controller 217 controls ion beamsource 203 to vary one or more ion beam properties, such as beamcurrent, beam energy, beam profile, any other suitable ion beamproperties, or combinations thereof. Controller 217 further controlsparameters, e.g., the scanning frequency, of the scanning operation ofscanning device 212. Controller 217 is also coupled to end station 213to control one or more of workpiece transfer and chuck movement. Forexample, controller 217 can control, for example, the velocity of themotors of wafer handling unit 215, which, in turn, control the velocityof wafer 223 with respect to coherent ion beam 221. In some embodiments,controller 217 is coupled to scanning device 212 provided within oradjacent to final energy magnet 211 to receive and/or determine ionenergy spectrum information for adjusting the final energy magnet orother components of ion implanter 200. In some embodiments, controller217 is one or more computers or microprocessors programmed to performone or more functions, such as calibrating or normal operating.Controller 217 can be implemented in either hardware or software, andthe parameters can be hardcoded or fed into controller 217 through oneor more input ports. Controller 217 can be coupled to components of ionimplanter 200 through any suitable means, such as one or more electricalcords 219.

FIG. 3 illustrates a table 300 listing exemplary ion implantationcalibration recipes used in an exemplary calibration process for an ionimplantation apparatus. As illustrated in FIG. 3, calibration recipesinclude recipes for various ions, such as boron, argon, and xenon.Recipes for any other suitable ions can be includes, in someembodiments. These exemplary ion implantation calibration recipes can beused to calibrate a single ion implanter, or multiple ion implanters, ina fabrication line to maintain agreement across multiple implanters.Each ion implantation calibration recipe can include suitable parametersfor providing ions imparted with nominal ion energy before bombardingsemiconductor substrates. In some embodiments, ion implantationcalibration recipe can include nominal ion energy for desired forvarious ions, such as boron, argon, arsenic, xenon, and/or any othersuitable ions. In some embodiments, nominal ion energy includessingle-charged boron ions (B⁺) having energy 10 keV, single-chargedargon ions (Ar⁺) having energy 80 keV, triply-charged xenon ions (Xe³⁺)having energy 1890 keV, triply-charged xenon ions (Xe³⁺) having energy2430 keV, and any other suitable ions and ion energy. For example,nominal ion energy for single-charged boron ions (B⁺) can have energybetween about 8 keV to about 12 keV. In some embodiments, nominal ionenergy for single-charged boron ions (B⁺) can have energy from about 8keV to about 9 keV, about 9 keV to about 10 keV, about 10 keV to about11 keV, about 11 keV to about 12 keV. For example, nominal ion energyfor single-charged argon ions (Ar⁺) can have energy from about 64 keV toabout 96 keV. In some embodiments, nominal ion energy for single-chargedargon ions (Ar⁺) can have energy from about 64 keV to about 72 keV,about 72 keV to about 80 keV, about 80 keV to about 88 keV, about 88 keVto about 96 keV. For example, nominal ion energy for triply-chargedxenon ions (Xe³⁺) can have energy from about 1512 keV to about 2268 keV.In some embodiments, nominal ion energy for triply-charged xenon ions(Xe³⁺) can have energy from about 1512 keV to about 1701 keV, about 1701keV to about 1890 keV, about 1890 keV to about 2079 keV, about 2079 keVto about 2268 keV. For example, nominal ion energy for triply-chargedxenon ions (Xe³⁺) can have energy from about 1944 keV to about 2916 keV.In some embodiments, nominal ion energy for triply-charged xenon ions(Xe³⁺) can have energy from about 1944 keV to about 2187 keV, about 2187keV to about 2430 keV, about 2430 keV to about 2673 keV, about 2673 keVto about 2916 keV. Ion implantation calibration recipe can also includeother suitable information, such as, name of ion implantation recipe,mass of an atom expressed in atomic mass unit, nominal ion beamcondition during calibration process, and other suitable information. Insome embodiments, the ion implantation recipe also include calibrationthreshold information, for example, a maximum energy gap between anominal ion energy required by ion implantation recipe and ion energydetected by final energy magnet. In some embodiments, examples of finalenergy magnet can be final energy magnet 211 described above in FIG. 2.Detailed calibration process of ion implanter 200 is further describedbelow with reference to FIGS. 4-8.

FIG. 4 is a flow diagram of an exemplary method 400 for calibrating oneor more ion implanters, in accordance with some embodiments of thepresent disclosure. Other operations in method 400 can be performed andoperations of method 400 can be performed in a different order and/orvary. FIGS. 5-8 are provided as exemplary energy spectrum diagrams tofacilitate in the explanation of method 400.

At operation 402, an ion implantation calibration recipe is loaded intoan ion implanter, in accordance with some embodiments of the presentdisclosure. Examples of the ion implanter can be ion implanter 200described above in FIG. 2. Examples of ion implantation the calibrationrecipe can be ion implantation recipes described above in FIG. 3. Insome embodiments, the ion implantation calibration recipe can be loadedinto ion implanter 200 by controller 217 to generate and accelerateselected ions to a nominal ion energy.

At operation 404, ion implanter 200 can generate and accelerate ionsusing an accelerator to a nominal ion energy based on the ionimplantation calibration recipe, in accordance with some embodiments ofthe present disclosure. In some embodiments, ion source 203 of FIG. 2generates an ion beam that includes ions having a range ofcharge-to-mass ratio and ion energy suitable for implantation. Forexample, ion source 203 can generate boron ions, arsenic ions, argonions, xenon ions, and any other suitable ions based on the ionimplantation calibration recipe. In some embodiments, ion source 203 cangenerate high energy Xe³⁺ ions for calibration purposes. In someembodiments, Xe³⁺ ions are used in the calibration process rather thanXe⁺ ions which are used in a normal operation process for semiconductorwafers. In a normal operation process, Xe⁺ ions are generated andaccelerated using both accelerator of ion source 203 and linearaccelerator 209 to achieve a nominal high ion energy, e.g., 1890 keV or2430 keV. However, in a calibration process, linear accelerator 209 isconfigured as a pass through without providing ion acceleration. Forexample, RF cavities of linear accelerator 209 can be turned off duringa calibration process and Xe³⁺ ions can achieve a nominal ion energy inaccordance with nominal ion energies by only using the DC accelerator inion source 203. In some embodiments, single-charged xenon ions can beused for calibration purposes.

At operation 406, an energy spectrum of ion beam passing through thefinal energy magnet is generated, in accordance with some embodiments ofthe present disclosure. Final energy magnet 211 of FIG. 2 can removeions or neutral particles that have been generated with an incorrectenergy during the acceleration processes. An ion beam energy spectrumdetected at final energy magnet 211 can represent the energydistribution and peak energy of the ion beam allowed to pass throughfinal energy magnet 211. By adjusting the magnetic field strength, finalenergy magnet 211 removes ions from coherent ion beam 221 that haveincorrect energy and allows ions having the correct energy pass through.For example, final energy magnet 211 can adjust its magnetic field byapplying different electrical currents to its magnet coils. In someembodiments, ion beam energy spectrum is determined by a scanner deviceplaced within final energy magnet 211. In some embodiments, ion beamenergy spectrum is determined by scanner device 212 placed after finalenergy magnet 211.

At operation 408, an ion energy difference between ion energy obtainedat the final energy magnet and ion energy specified in the ionimplantation calibration recipe is determined, in accordance with someembodiments of the present disclosure. Controller 217 can be configuredto receive ion energy spectrums from corresponding components of ionimplanter 200 and determine ion energy differences by comparing ionenergy at the final energy magnet and ion energy measured at upstreamscanner device 207 placed after the analysis magnet unit. Using recipe“B+10 k” provided in FIG. 3 as an example, the ion energy specified inthe calibration recipe can be a starting point for the calibrationprocess. In some embodiments, analysis magnet unit 205 or upstreamscanner device 207 can provide an ion energy spectrum based on ion beam206 and used as starting point for the calibration process.

The ion energy spectrum determined by scanner device 212 of calibrationrecipe “B+10 k” is shown as ion energy spectrum 501 illustrated in FIG.5. Ion energy spectrum 501 illustrates the ion energy distribution andpeak ion energy of ion beam processed by final energy magnet 211 andprior to calibration. Controller 217 can be configured to determine peakenergy of the ion energy spectrum at final energy magnet 211, determinean ion energy difference between the determined peak energy, compare thepeak energy with the ion energy specified by the calibration recipe, anddetermine whether the energy difference is within a predetermined value.For example, controller 217 can be configured to determine peak energyof ion energy spectrum 501, illustrated by a dashed line 503intersecting with the x-axis at 11.2 keV. As described above,calibration recipe “B+10 k” specifies a peak energy of 10 keV;therefore, controller 217 can be configured to determine an ion energydifference, or error gap, ΔE₁ to be the difference between peak energyof ion energy spectrum and energy specified by the calibration recipedivided by the energy specified by the calibration recipe (or ion energydetermined by upstream scanner device 207). In this scenario, ΔE₁=(11.2keV−10 keV)/10 keV=1.2%. The predetermined value can be a maximum energydifference permitted between the ion energy of ion beam at final energymagnet 211 and an ion energy specified by the calibration recipe. Forexample, the predetermined value can be about 1%, which is of the ionenergy difference divided by the energy specified in the calibrationenergy or ion energy detected of ion beam 221 detected by upstreamscanner device 207. In some embodiments, the predetermined value can be0.5%, 3%, 5%, or any other suitable value determined by the need of theion implantation process. Since the predetermined value represents theallowed energy difference between an detected ion energy and a nominalion energy, a lower predetermined value provides a more precisecalibration process. In some embodiments, calibration recipes canspecify any suitable peak energies or range of peak energies, and thepredetermined value can be a maximum energy difference permitted betweenthe ion energy of ion beam and the range of ion energy specified by thecalibration recipe. For example, calibration recipe “B+10 k” can alsospecify peak energy between about 9 keV and about 11 keV. In someembodiments, calibration recipe can specify peak energy between about 9keV and about 10 keV, between about 10 keV to about 11 keV.

At operation 410, one or more calibration parameters of the final energymagnet is adjusted such that the ion energy difference between ionenergy detected at final energy magnet and ion energy specified in thecalibration recipe is within the predetermined value, in accordance withsome embodiments of the present disclosure. Using calibration recipe“B+10 k” described above in operation 408 as an example, the ion energydifference ΔE₁ can be 1.2%, which is greater than the predeterminedvalue of about 1%. By adjusting one or more calibration parameters offinal energy magnet 211, the ion energy difference ΔE₁ can be reduced toless than the predetermined value. For example, based on the determinedion energy difference ΔE₁, the controller 217 can be configured toadjust the electrical current (e.g., beam control current) that controlsthe magnetic field of final energy magnet. Controller 217 can be furtherconfigured to determine the ion energy difference ΔE₁ after theadjustment and maintain the electrical current in response to ion energydifference ΔE₁ being within the predetermined value. In someembodiments, any other suitable calibration parameters can be adjusted.In some embodiments, controller 217 can adjust any suitable parameterssuch that the ion energy difference ΔE₁ can successfully be within thepredetermined value. As shown in FIG. 5, ion energy spectrum 505illustrates ion energy spectrum of the ion beam after controller 217adjusts one or more calibration parameters such that the ion energydifference is within the predetermined value, such as about 1%. Ionenergy spectrum 505 of the ion beam provided by calibrated final energymagnet 211 illustrates a peak energy of ion energy spectrum 505,illustrated by a dashed line 507 intersecting with the x-axis at 10 keV.In some embodiments, the suitable parameters can be beam control currentof the FEM. In some embodiments, the predetermined value can be anysuitable value determined by implantation need. For example, thepredetermined value can be about 0.5%, about 1.5%, about 2%, or anyother suitable value.

At operation 412, the adjusted one or more calibration values of thefinal energy magnet for a calibration recipe is saved, in accordancewith some embodiments of the present disclosure. Controller 217 can beconfigured to store the adjusted one or more calibration values of thefinal energy magnet in a storage device and control the final energymagnet during normal operation using the stored adjusted one or morecalibration values. Controller 217 can include a computer system thatincludes a microprocessor, an input device, a storage device, a systemmemory, a display, and a communication device all interconnected by oneor more buses. In some embodiments, controller 217 can be configured toreceive user input directly from the input device. The storage devicecan be a hard drive, an optical device, and/or any other suitablestorage device. The storage device can be capable of receiving CD-ROM,DVD-ROM, USB storage device, or any suitable forms of computer-readablemedium that may include computer-executable instructions. Aftercalibration of one calibration recipe is completed, another recipe canbe loaded into ion implanter 200 and the final energy magnet can becalibrated in a fashion similar to operations 402 through 412.

FIGS. 6-8 illustrate ion energy spectrums after calibration for variouscalibration recipes, in accordance with some embodiments of the presentdisclosure. FIGS. 6-8 illustrate ion energy spectrum diagrams determinedby scanner device 212 after calibration of calibration recipe “Ar+80 k,”“Xe+++70 k,” and “Xe+++90 k” of list of recipes shown in FIG. 3,respectively. In FIG. 6, the ion energy spectrum determined by scannerdevice 212 of calibration recipe “Ar+80 k” is shown as ion energyspectrum 601 illustrated in FIG. 6. Ion energy spectrum 601 illustratesthe ion energy distribution and peak ion energy of ion beam processed byfinal energy magnet 211 and after calibration. Ion energy spectrum 601of the ion beam provided by calibrated final energy magnet 211illustrates a peak energy of ion energy spectrum, illustrated by adashed line 603 intersecting with the x-axis at 80.4 keV. During thecalibration process, controller 217 can be configured to determine peakenergy of the ion energy spectrum at final energy magnet 211, determinean ion energy difference between the determined peak energy, compare thepeak energy with the ion energy specified by the calibration recipe, anddetermine whether the energy difference is within a predetermined value.After the calibration process, controller 217 can be configured todetermine whether an ion energy difference, or error gap, ΔE₂ is withina predetermined value, such as about 1% of the ion energy specified inthe calibration recipe or ion energy detected at upstream scanner device207. In this scenario, ΔE₂=(80.4 keV−80 keV)/80 keV=0.5%, therefore theenergy difference or error gap satisfies the predetermined value andcontroller 217 can store the calibrated system parameters and move on toload the next calibration recipe if needed.

In FIG. 7, the ion energy spectrum determined by scanner device 212 ofcalibration recipe “Xe+++70 k” is shown as ion energy spectrum 701 whichillustrates the ion energy distribution and peak ion energy of ion beamprocessed by final energy magnet 211 and after calibration. Ion energyspectrum 701 of the ion beam provided by calibrated final energy magnet211 illustrates a peak energy of ion energy spectrum, illustrated by adashed line 703 intersecting with the x-axis at 1909 keV. After thecalibration process, controller 217 can be configured to determinewhether an ion energy difference, or error gap, ΔE₃ is within apredetermined value, such as about 1% of the ion energy specified in thecalibration recipe or ion energy detected at upstream scanner device207. In this scenario, ΔE₃=(1909 keV−1890 keV)/1890 keV=1.0%, thereforethe energy difference or error gap satisfies the predetermined value andcontroller 217 can store the calibrated system parameters and move on toload the next calibration recipe if needed.

In FIG. 8, the ion energy spectrum determined by scanner device 212 ofcalibration recipe “Xe+++90 k” is shown as ion energy spectrum 801 whichillustrates the ion energy distribution and peak ion energy of ion beamprocessed by final energy magnet 211 and after calibration. Ion energyspectrum 801 of the ion beam provided by calibrated final energy magnet211 illustrates a peak energy of ion energy spectrum, illustrated by adashed line 803 intersecting with the x-axis at 2445 keV. After thecalibration process, controller 217 can be configured to determinewhether an ion energy difference, or error gap, ΔE₄ is within apredetermined value, such as about 1% of the ion energy specified in thecalibration recipe or ion energy detected at upstream scanner device207. In this scenario, ΔE₄=(2445 keV−2430 keV)/2430 keV=0.6%, thereforethe energy difference or error gap satisfies the predetermined value andcontroller 217 can store the calibrated system parameters and move on toload the next calibration recipe if needed.

FIGS. 9-10 illustrate exemplary results of wafer acceptance testsshowing improved agreements between multiple ion implanters after thecalibration processes, in accordance with some embodiments of thepresent disclosure. FIG. 9 illustrates sheet resistance of a pluralityof wafers processed by ion implanters Tools A-F prior to the calibrationprocess described above with reference to operations 402 through 412. Asshown in FIG. 9, reference resistance value 901 is used as a referencepoint and sheet resistance values 903-913 represent measured sheetresistances on Tools A-F, respectively. Prior to ion implantercalibration, the sheet resistance values 903-913 are determined to bewithin 2 sigma (i.e., two standard deviations) of reference resistancevalue 901, which can cause long term resistance reference shift andmismatching between a line of ion implanter tools. However, using thecalibration process described above in operations 402-412, mismatch canbe reduced and improved agreement is maintained between ion implanters.FIG. 10 includes wafer sheet resistance values of wafer processed bycalibrated Tools A-F. For example, FIG. 10 includes reference resistancevalue 1001 and sheet resistance values 1003-1013 representing measuredsheet resistances on Tools A-F, respectively. After ion implantercalibration, the sheet resistance values 1003-1013 are determined to bewithin 1 sigma (i.e., one standard deviation) of reference resistancevalue 1001, which indicates improved precision and agreement between ionimplanters.

Various embodiments in accordance with this disclosure describe systemsand methods for calibrating high energy implanters for use insemiconductor wafer processing, and more particularly to systems andmethods for modifying and calibrating a final energy magnet of a highenergy implantation apparatus. The present disclosure provides systemsand methods for improving wafer acceptance tests by determining energygaps between the recipe energy and determined energy of the ion beam andcalibrating the high energy implantation apparatus accordingly based onthe determined energy gap. The calibration system determines target massand ion beam energy after ions are accelerated and selected by theanalysis magnet unit. The calibration system further determines a totalenergy amount when an ion beam passes through a linear accelerator andthrough a final energy magnet. The calibration system further determinesthe error gap between recipe energy and determined energy using the ionbeam spectrum at the final energy magnet. In some embodiments, theenergy difference or error gap is within about 1% of the energyspectrum. The calibration system can be implemented in one or more highenergy implantation apparatus to maintain good agreement across allimplanters.

In some embodiments a method includes generating ions with an ion sourceof an ion implantation apparatus based on an ion implantation recipe.The method includes accelerating the generated ions based on an ionenergy setting in the ion implantation recipe and determining an energyspectrum of the accelerated ions. The method also includes analyzing arelationship between the determined energy spectrum and the ion energysetting. The method further includes adjusting at least one parameter ofa final energy magnet (FEM) of the ion implantation apparatus based onthe analyzed relationship.

In some embodiments a method for calibrating an ion implantationapparatus includes loading an ion implantation recipe in the ionimplantation apparatus and generating ions by an ion source based on theion implantation recipe. The method includes accelerating the ions basedon an ion energy setting in the ion implantation recipe and determiningan energy spectrum of the accelerated ions at a final energy magnet(FEM) of the ion implantation apparatus. The method also includesdetermining a peak energy of the energy spectrum and determining adifference between the peak energy and the ion energy setting. Themethod further includes adjusting at least one parameter of the FEMbased on the difference being greater than a predetermined value.

In some embodiments, an ion implantation apparatus includes an ionsource configured to accelerate ions based on an ion implantation recipeand a final energy magnet (FEM) configured to determine an energyspectrum of the accelerated ions and to determine a peak energy of theenergy spectrum. The apparatus further includes a controller configuredto determine a difference between the peak energy and an ion energysetting in the ion implantation recipe and to adjust at least oneparameter of the FEM based on the difference being greater than apredetermined value.

It is to be appreciated that the Detailed Description section, and notthe Abstract of the Disclosure, is intended to be used to interpret theclaims. The Abstract of the Disclosure section may set forth one or morebut not all exemplary embodiments contemplated and thus, are notintended to be limiting to the subjoined claims.

The foregoing disclosure outlines features of several embodiments sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art will appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodimentsintroduced herein. Those skilled in the art will also realize that suchequivalent constructions do not depart from the spirit and scope of thepresent disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the subjoined claims.

What is claimed is:
 1. A method, comprising: determining an energyspectrum of accelerated ions produced by an ion implantation apparatus;analyzing a relationship between the determined energy spectrum and anion energy setting of the ion implantation apparatus; and adjusting atleast one parameter of a final energy magnet (FEM) of the ionimplantation apparatus based on the analyzed relationship.
 2. The methodof claim 1, wherein the at least one parameter comprises a beam controlcurrent of the FEM.
 3. The method of claim 1, further comprisingdetermining a peak energy of the determined energy spectrum.
 4. Themethod of claim 3, wherein the relationship comprises a differencebetween the peak energy and the ion energy setting.
 5. The method ofclaim 4, wherein the adjusting the at least one parameter comprisesadjusting the at least one parameter such that the difference betweenthe peak energy and the ion energy setting is less than a predeterminedvalue.
 6. The method of claim 5, wherein the predetermined valuecomprises an energy difference of about 1% of the ion energy setting. 7.The method of claim 5, wherein the predetermined value comprises anenergy difference of about 3% of the ion energy setting.
 8. The methodof claim 5, wherein the predetermined value comprises an energydifference of about 5% of the ion energy setting.
 9. The method of claim1, further comprising maintaining the at least one parameter based onthe analyzed relationship.
 10. The method of claim 1, wherein thegenerated ions comprise xenon ions.
 11. A method, comprising:determining an energy spectrum of accelerated ions at a final energymagnet (FEM) of an ion implantation apparatus; determining a first peakenergy of the energy spectrum; determining a first difference betweenthe first peak energy and an ion energy setting of the ion implantationapparatus; and adjusting at least one parameter of the FEM in responseto the first difference being greater than a predetermined value. 12.The method of claim 11, wherein adjusting the at least one parametercomprises adjusting a beam control current of the FEM.
 13. The method ofclaim 11, further comprising; determining a second peak energy of theenergy spectrum and a second difference between the second peak energyand the ion energy setting; and maintaining the at least one parameterof the FEM in response to the second difference being less than thepredetermined value.
 14. The method of claim 13, further comprisingloading an ion implantation recipe in the ion implantation apparatus inresponse to the second difference being less than the predeterminedvalue.
 15. The method of claim 11, wherein the adjusting the at leastone parameter comprises adjusting the first difference between the firstpeak energy and the ion energy setting to be less than the predeterminedvalue.
 16. An apparatus, comprising: a final energy magnet (FEM)configured to determine a peak energy of an ion energy spectrum; and acontroller configured to determine a difference between the peak energyand a preset ion energy setting and to adjust at least one parameter ofthe FEM based on the difference being greater than a predeterminedvalue.
 17. The apparatus of claim 16, wherein the at least one parametercomprises a beam control current of the FEM.
 18. The apparatus of claim16, wherein the controller is further configured to load an ionimplantation recipe in the apparatus in response to the difference beingless than the predetermined value.
 19. The apparatus of claim 16,wherein the controller is further configured to adjust the at least oneparameter such that the difference between the peak energy and the ionenergy setting is less than the predetermined value.
 20. The apparatusof claim 16, wherein the predetermined value comprises an energydifference of about 1% of the ion energy setting.